Kai Ni

Soochow University · School of Rail Transportation

Thanks to the dc-biased sinusoidal current excitation, the flux modulated doubly-salient reluctance motor (FMDRM) drive is endowed with the zero-sequence voltage (ZSV) regulation ability to achieve dc-biased current control. The open-winding converter with a common dc bus is widely utilized and the ZSV regulation is achieved by redistributing the d...

Owing to the significant torque ripple and vibration reduction ability, flux-modulated doubly-salient reluctance motor (FMDRM) drives have been widely investigated. However, the parallel dual-inverter is commonly utilized in conventional FMDRM drives, where the power switch number is doubled compared to conventional ac motor drives. In this paper,...

In traditional space vector pulse width modulation (SVPWM) scheme, the duration of zero vector (vector 0, vector 7) is equally divided. On this occasion, the corresponding control freedom is wasted, since the zero vector distribution exerts an influence on the current ripple without affecting the total voltage vector synthesis. Accordingly, this pa...

In a hybrid-inverter open-winding permanent magnet synchronous motor (OW-PMSM) drive, the motor and the floating capacitor are controlled simultaneously. Besides, since the compensatory inverter barely provides active power under steady-state operation, the unity power factor control (UPFC) of the main inverter (MI) is also required. However, the c...

This paper proposes a wireless open-winding motor (WOWM) system, where noncontact operation can be achieved with the magnetic coupler. Thus, the flexibility and reliability of the WOWM system can be improved. Two isolated DC voltage ports for the open-winding motor can be obtained with only one DC voltage source, which facilitates the application o...

This paper proposes a novel dc-link voltage regulation (DCVR) strategy for the series-series compensated wireless motor (SSWM) system. The steady-state voltage control is presented to optimize the system efficiency and the feedforward voltage boost control is proposed to improve system resilience. The rated capacity identification (RCI) scheme is p...

Doubly fed induction generators (DFIGs) are widely applied in wind energy conversion systems, where the harsh service environment and long-lasting operation can bring about motor parameter deviations, deteriorating the system performance. In this paper, an extended state observer (ESO)-based deadbeat control strategy that enhances the system parame...

This brief proposes an eigenfrequency identification scheme (EIS) based on circuit theory in time domain for a series-parallel compensated wireless power transfer (SP-WPT) system with the pure capacitance filter. In the SP-WPT system, the high nonlinear features (HNFs), including the strong magnetic coupling and diode rectifier influence the system...

In this paper, a novel phase current reconstruction strategy for a Five-Leg Dual-Inverter (FL-DI) fed Open-Winding Permanent Magnet Synchronous Motor (OW-PMSM) drive is put forward. Benefiting from the doubling of the power legs, the OW-PMSM drive is endowed with outstanding fault-tolerant ability. When an open-circuit fault occurs, the OW-PMSM aut...

A power compensated triple-vector model predictive direct power control (PCTV-MPDPC) strategy is proposed in this paper for non-redundant fault-tolerant three-phase rectifiers. The system fault tolerance ability and post-fault control performance are enhanced with low hardware complexity. By defining the negative conjugate of complex power as the c...

Compared to the conventional doubly-salient reluctance motor (DRM) drives, the novel flux modulated DRM (FMDRM) drives can achieve a better overall torque performance due to the dc-biased sinusoidal current excitation. However, previous investigations only focus on the dc-biased and fundamental current components, and the contributions of current h...

The existing energy modulation simultaneous wireless power and data transfer (EM-SWPDT) system will cause severe load voltage drop and power efficiency reduction at the data transmitting. Besides, those methods can only achieve simplex communication. To solve these problems, this article proposes a single coil half-duplex communication EM-SWPDT sys...

A novel phase current reconstruction method is present in this paper for the flux modulated doubly-salient reluctance motor drive without phase shift. Conventionally, each phase current must be sampled individually with different sensors as the zero-sequence current (ZSC) excitation is required, which significantly increases the system cost. Beside...

In this paper, a computationally efficient cascaded model predictive control (CMPC) is put forward for the hybrid-inverter fed open-winding permanent magnet synchronous motor (OW-PMSM) drive, which significantly reduces the computational burden and eliminates the weighting factors. The hybrid-inverter consists of a main inverter (MI) and a compensa...

The wireless heat transfer (WHT) system is proposed to ensure the reliability and flexibility of the electrical heat tracing for domestic and industrial applications. In this article, the inherent coupling relationship among coil dimension, resistance, distance, and inductance of a WHT system is investigated, which illustrates the intrinsic link be...

At present, research of cable fault diagnosis based on artificial intelligence mainly takes statistical characteristics as inputs, which means the appropriateness of statistical characteristic selection is directly related to the diagnosis accuracy and the identification results may have certain contingency. Further, most of these methods do not co...

In this paper, a novel instantaneous electromagnetic torque modeling technique and current component distribution strategy are proposed for torque ripple reduction in three-phase flux modulated doubly-salient reluctance motor (FMDRM) drives. Firstly, the analytical model of the instantaneous electromagnetic torque of a three-phase FMDRM is establis...

In this paper, a simplified pulse width modulation (PWM) strategy is proposed for open-winding flux modulated doubly-salient reluctance motor (FMDRM) drives for switching action minimization and common-mode voltage (CMV) reduction. Conventionally, the open-winding converter topology is utilized to achieve the zero-sequence current flow path and dc-...

For the open winding permanent magnet synchronous motor (OW-PMSM) with leg open-circuit faults, a novel zero-sequence current (ZSC) suppression method with asymmetric zero-sequence voltage (ZSV) injection is proposed in this paper. To realize the fault-tolerant control (FTC) in leg open-circuit fault conditions, the leg-sharing method is developed,...

This article proposes a real-time maximum power efficiency tracking (MPET) scheme for a series−parallel compensated wireless motor (SP-WM) system, where the system efficiency is maximized based on real-time manipulation of the dc-link voltage. The transient performance of the motor and stability of the dc-link voltage can be improved by SP compensa...

DC-biased sinusoidal current excited flux modulated doubly-salient reluctance motor (FMDRM) drives are developed to reduce the torque ripple and vibration of doubly-salient reluctance motors (DRMs). Conventionally, because of the discontinuous quasi-square current excitation, the rotor position of DRMs is estimated by the combination of piecewise e...

In this paper, a novel current error calibration scheme considering noncentral sampling is proposed for an open winding permanent magnet synchronous motor (OW-PMSM) drive with a single current sensor. To realize the current reconstruction using a single current sensor, the durations of measurement vectors need to last long enough. Besides, the puls...

This paper proposes a virtual current constraint based segmented trajectory control strategy for surface-mounted permanent-magnet synchronous motor (SPMSM) drives, to improve the transient performance under the flux-weakening operation. In the conventional scheme, the operating points (OPs) are arranged on the current constraint circle during the s...

This paper proposes a modular seven-leg switched reluctance motor (SRM) drive with flexible winding configuration and fault-tolerant capability. In traditional SRM drives, the winding connection is fixed, where the speed regulation range and fault-tolerant ability are both limited. To solve these issues, a modular seven-leg drive topology is propos...

This paper proposes a phase current reconstruction strategy for open-winding synchronous reluctance motor (OW-SynRM) drives with the dual-inverter topology and common dc bus. The traditional reconstruction strategy cannot be applied in OW motor drives, because the dual-inverter modulation and zero-sequence current (ZSC) suppression strategies compl...

For safety critical transportation applications like all-electric ship propulsion systems (SPS), the reliable system operation is definitely the primary concern. In this paper, a fault-tolerant back-to-back power converter based on the four-switch three-phase (FSTP) topology is applied to a doubly-fed induction machine (DFIM) based all-electric SPS...

This paper proposes a novel dual three-phase flux-modulated switched reluctance motor (SRM) drive with maximum torque per ampere (MTPA) capability. Different from the existing open-winding structure, the stator winding is in dual three-phase connection, which effectively eliminates the side effects of the zero-sequence harmonic voltage component. H...

A doubly-fed induction machine (DFIM) is a promising choice for the shipboard propulsion system (SPS) of a more-electric ship (MES) to increase the system safety level by employing less power electronics. In this paper, the detailed impedance model of DFIM-SPS is established, with a salient-pole synchronous generator (SPSG) acting as the power sour...

The communication system of a microgrid can transfer the information of electricity price, power consumption and so on between users and the control centre. This capability is of great significance to improve the efficiency and sustainability of power facilities. In this paper, a bidirectional DC–AC converter topology is proposed to achieve the com...

With the partially power decoupled system architecture, a doubly-fed induction motor-based shipboard propulsion system (DFIM-SPS) has the potential of increasing the system safety level by decreasing the penetration of power electronics. In this paper, a phase-locked-loop-free (PLL-free) direct power control (DPC) strategy is proposed for a DFIM-SP...

To lower the difficulty of fault protection, a doubly-fed induction machine based shipboard propulsion system (DFIM-SPS) that is partially power decoupled is presented. In such an intrinsically safe SPS architecture, a synchronous generator (SG) is employed for power generation, and the accuracy of the parameters of power generation unit (PGU) play...

The dilemma between high control performance and high fault tolerance for a power electronic penetrated shipboard propulsion system (SPS) impedes the development of more-electric ships (MESs). In this paper, with a doubly-fed induction machine (DFIM) electric drivetrain adopted, a partially power decoupled SPS structure is presented to enhance the...

This paper proposes a simplified dual-electric-port drive for a flux-modulated switched reluctance machine (SRM) with flexible charging capability for electric vehicle (EV) applications. In the driving mode, the developed flux modulation control can be achieved by directly employing the modular three-phase full-bridge converter compared to the conv...

This paper proposes a comprehensive investigation method for loss calculation and temperature rise prediction in high-speed and high-power switched reluctance machines (SRMs). The losses are analyzed in details and the sequential iterative fluid-solid coupling (SIFSC) scheme is proposed for thermal analysis. In the iterative design stage of the SRM...

Hybrid vehicle is an important development direction of the automobile industry to solve environmental problems. A switched reluctance motor (SRM) is one of the main choices for its drive system. A novel converter topology of SRM is designed in this paper. The novel converter can realize multi-level control and battery energy management. The batter...

This study proposes an investigation scheme of the rotor strength and rotor dynamic characteristics for high‐speed high‐power switched reluctance machines (SRMs). The analytical model and finite element analysis model are established to predict the maximum stress and deformation in the rotor. The Mises yield criterion is employed to verify the stre...

In order to meet the working requirements of high performance and low cost for a photovoltaic (PV) aircraft driven by switched reluctance motors (SRMs), a multiport driving topology (MDT) is proposed. The converter is composed of an asymmetric half-bridge and a multiport power source circuit. Three driving and two charging modes can be realized thr...

This paper develops a high-performance finite control set model predictive current control (FCS-MPCC) method for induction motors (IM) to ensure the system control performance over the lowswitching- frequency (LSF) range, where the switching loss is low. The new controller is based on tripartite calculations in each control period and sliding mode...

With less fragile power electronics integrated, the overall shipboard power system (SPS) safety level is prone to increase. In this paper, the motion equation concept of a less power electronics-based more-electric ship is proposed to study the SPS dynamics. A wound rotor induction machine (WRIM) acts as the propulsion load, whose stator and power...

Identifying the air-gap flux is a prerequisite for realizing the decoupling control between air-gap flux and torque in an electrically excited synchronous motor (EESM) vector control system. For the nonlinear problem of electrically excited synchronous motor, the frequency response function method is introduced to analyze the air-gap flux voltage a...

Over the past few years, interest and research in wireless power transfer (WPT) have been rapidly incrementing, and as an effect, this is a remarkable technology in many electronic devices, electric vehicles and medical devices. However, most of the applications have been limited to very close distances because of efficiency concerns. Even though t...

With the increasing demand of applications that have two different output voltages, the single-input dual-output (SIDO) converter with fewer components is becoming the cost-effective option instead of employing two single-input single-output converters. However, the cross regulation of different outputs is still a challenge in SIDO converters desig...

The precision of position estimation is highly dependent on the accuracy of multiple current sensors. Whereas the conventional error calibration strategies for current sensor accuracy uncertainty (SAU) problem have limitations regarding the position sensorless controlled drives. In order to solve this thorny problem, this paper proposes a mutual ca...

In order to enhance the dynamic performance of the surface-mounted permanent magnet synchronous machines (PMSM), this paper proposes a novel finite control set (FCS) model predictive direct speed control (MPDSC) strategy that only contains one speed control loop. In comparison with the traditional two-step prediction method, the new controller is a...

Nowadays, the fully power decoupled shipboard power system (SPS) architecture is popular. However, the volume of fragile power electronic converters is large, and the system overload capability is low. In this paper, an asynchronized synchronous motor (ASM) based SPS is proposed for more-electric ships (MESs) to handle these issues. The models of s...

The advancement in power electronics techniques provides strong impetus for the adoption of medium-voltage direct current (MVDC) shipboard power system (SPS). However, high fault protection difficulty and cost are the major challenges. In this paper, a partially power decoupled SPS based on doubly-fed induction machine (DFIM) propulsion load is pre...

In order to improve the performance of switched reluctance motor (SRM) systems for photovoltaic (PV) pumps, this paper introduces a new converter topology for SRM with controllable multiple power sources. Only simple switching components need to be added at the front end of the asymmetric half-bridge converter in this topology, which enables the co...

This paper presents a review of the electrical and electronic technologies investigated in more-electric aircraft (MEA). In order to change the current situation of low power efficiency, serious pollution, and high operating cost in conventional aircraft, the concept of MEA is proposed. By converting some hydraulic, mechanical, and pneumatic power...

Drilling is traditionally performed by multi-motor systems manually. However, the complex intermediate transmission mechanisms in the traditional design have large size and relatively low robustness. In this paper, a split-stator 2-degree-of freedom (2DoF) machine is applied. By conducting linear, rotary, and helical motion by only one machine, it...

The 2-degree-of-freedom direct drive induction motor (2DoFDDIM) is capable of implementing rotary, linear or helical motion, which has the definite advantages of integrated structure, high material utilization and so on. In this paper, the characteristics analysis of the three kinds of motions are presented. The air-gap magnetic field distributions...

When an emergency happens to electric vehicles, the voltage of the DC-bus capacitor which is an important part of the permanent magnet synchronous machine (PMSM) drive system requires to be reduced as quickly as possible. Recently, a new idea of directly using the windings to discharge the capacitor has come forth. This paper proposes a physical en...

Hybrid electrical vehicle (HEV) is a popular transport solution to reducing carbon dioxide emissions. Switched reluctance motors (SRMs) are one of the most promising motors for such applications. In SRM-based series type HEV, there are three energy components, i.e., generator, battery bank, and SRM. A tri-port converter is needed to combine the thr...

In this paper, a highly reliable back-to-back (BTB) power converter is proposed for doubly-fed induction generator-based wind turbines (DFIG-WTs). When a power switch open-circuit fault is encountered in either the grid-side converter (GSC) or rotor-side converter (RSC), a four-switch three-phase (FSTP) topology is formed to avoid using redundant b...

This study presents a new portable eight-output light emitting diode (LED) driver. The eight output-channels are divided into two equal groups, and their output powers can be controlled individually by three active switches. In addition, a simple capacitor-based passive current balancing circuit (CBC) is employed in each port to guarantee that the...

The Switched Reluctance generator (SRG) has been widely used as a constant voltage source due to its advantages of simple structure, low cost and high control flexibility. However, the output voltage ripples cannot be ignored due to its unique operating principle with phase commutation. In this paper, the influence of the control parameters on the...

Modeling of a clinical lab carbon footprint is performed in this study from the aspects of electricity, water, gas consumption and waste production from lab instruments. These environmental impact indicators can be expressed in the form of the CO2 equivalent. For each type of clinical test, the corresponding consumption of energy resources and the...

To connect renewable energy sources (RESs) with a unity-grid, energy storage (ES) systems are essential to eliminate the weather fluctuation effect, and high voltage direct current (HVDC) transmission is preferred for large-scale RESs power plants due to the merits of low cost and high efficiency. This paper proposes a multi-port bidirectional DC/D...

Aging affects different photovoltaic (PV) modules in a PV array in a non-uniform way, thereby leading to non-uniform working conditions of the PV modules and resulting in variations in the power outputs of the PV array. In this paper, an algorithm is developed for optimising the electrical configuration of a PV array during the non-uniform aging pr...

High frequency signal injection (HFI) is an alternative method for estimating rotor position of interior permanent magnet synchronous motor (IPMSM). The general method of frequency and amplitude selection is based on error tolerance and experiments, and is usually set with only one group of HF parameters, which is not efficient for different workin...

The Switched Reluctance Generator (SRG) is suitable for wind power generation due to its good reliability and robustness. However, The SRG system adopting the conventional control algorithm with Pulse Width Modulation (PWM) method has a drawback, low response speed. The pulse train (PT) control has been widely used in dc/dc power converters operati...

To increase the reliability of a doubly-fed induction generator-based wind turbine (DFIG-WT), this paper proposes a fault-tolerant four-switch three-phase (FSTP) grid-side converter (GSC) with phase current reconstruction strategy. The proposed strategy is effective when the semiconductor open-circuit fault and phase current sensor failure occur si...

In high voltage direct current (HVDC) power transmission of offshore wind power systems, DC/DC converters are applied to transfer power from wind generators to HVDC terminals, and they play a crucial role in providing a high voltage gain, high efficiency, and high fault tolerance. This paper introduces an innovative multi-port DC/DC converter with...

Reliability is one of the critical issues for a modular multilevel converter (MMC) since it consists of a large number of series-connected power electronics submodules (SMs). In this paper, a complete control strategy including fault detection, localization, and tolerant operation is proposed for the MMC under an insulated gate bipolar transistor (...

This study proposes an open-end transformer-based power tap (OETPT) for the interconnection of the alternating current sub-grid and the direct current sub-grid of a hybrid micro-grid. Two topologies, topology-A and topology-B, were designed for OETPT, in which the primary or secondary windings of the transformer of OETPT are grounded, respectively....

As the phase current sensors and rotor speed/position sensor are prone to fail in the late stage of an offshore doubly-fed induction generator based wind turbine (DFIG-WT), this paper investigates a hybrid fault-tolerant strategy for a severe sensor failure scenario. The phase current sensors in the back-to-back (BTB) converter and the speed/positi...

In this paper, a multifunctional isolated and non-isolated dual-mode low-power converter was designed for renewable energy conversion applications such as photovoltaic power generation to achieve different operating modes under bi-directional electrical conversion. The proposed topology consists of a bidirectional non-isolated DC/DC circuit and an...

A hybrid fault scenario in a late-stage offshore doubly-fed induction generator (DFIG)-based wind turbine (DFIG-WT) with converter open-circuit fault and position sensor failure is investigated in this paper. An extended Kalman filter (EKF)-based sensorless control strategy is utilized to eliminate the encoder. Based on the detailed analysis of the...

This paper proposes a fundamental frequency sorting algorithm (FFSA) for balancing the floating capacitors in modular multilevel converters (MMCs) with low frequency carrier-phase-shift (CPS) modulation. The relationship between the driving pulses and sub-modules is re-built in every fundamental period by sorting the voltage increments and present...

With the rapid development and widespread applications of power electronic converters, strong fault-tolerant capability of power electronic converters is required since they play important roles in power systems. In this paper, a review of one of the most promising fault-tolerant topologies for semiconductor open-circuit fault, called four-switch t...

A new model of the optimum tilt angle of a soiled photovoltaic (PV) panel is proposed in this paper. The tilt angle is a key factor that influences the output power of PV panel, while dust deposition is an inevitable external element to be considered. In this paper, the solar radiation model is studied by analysing the Hay, Davies, Klucher, Reindl...

This paper investigates the performance of a fault-tolerant four-switch three-phase (FSTP) grid-side converter (GSC) in a doubly-fed induction generator-based wind turbine (DFIG-WT). The space vector pulse width modulation (SVPWM) technique is simplified and unified duty ratios are used for controlling the FSTP GSC. Steady DC-bus voltage, sinusoida...